Capacity estimation model of cluster tool in wafer fabrication
Abstract: Semiconductor manufacturing is a cost intensive industry particularly for modern 300mm manufacturing factories. Thus, production yield improvement is the most crucial issue to the manufacturing productivity correspondingly. Cluster tools are regarded as mainstream in modern semiconductor manufacturing factories over the past decade which dominated around 60% of production machines. Due to integrated by several components in a module and operated as a small factory, this kind of equipment increases the difficulty of production planning and shop floor control significantly because of complicated machine configurations. Moreover, for some small and middle scale semiconductor factories, managers will consider to combine un-relevant processes into one machine due to machine numbers and cost constraints. Thus, it will turn the difficulty of capacity estimation and planning into arduous challenge. In this work, the model of short term capacity planning for cluster tools is established. Three modules, WIP profile estimation, WIP schedule arrangement and capacity requirement calculation, are developed in this model. The concept of turn ratio is used to estimate the WIP penetration and forecast the WIP profile within a short time period. In order to reach the production goal of maximum output without exceeding time limit of product, Ec value of WIP is formulated. Based on WIP profile and Ec value of WIP, the expected recipe combination working on the equipment can be decided and the required capacity can be calculated as well.